1. Field
This disclosure relates generally to power delivery technologies in an electronic system, and more specifically but not exclusively, to controllers for power converters in an electronic system.
2. Description
As Integrated Circuits (“ICs”) (e.g., Digital Signal Processors (“DSPs”)) Circuits) in a computing platform become more power efficient, it is naturally desirable that a voltage regulator (“VR”) or a power delivery subsystem for such ICs becomes more energy efficient during power conversion at all load levels including light loads. Variable switching frequency combined with Discontinuous Conduction Mode (DCM) is used to improve converter efficiency at light loads. Such schemes may result in improved light load efficiency with no impact on high load efficiency but sometimes at the expense of degraded performance in terms of steady-state voltage ripple and dynamics. Other schemes such as non-linear control schemes are also proposed to meet the demand on performances while improving light load efficiency, but require additional detection of the peak inductor current in DCM.
Typically, a digital controller is used to control power delivery subsystem and to interface with ICs and other components in a digital system. A digital controller has advantages for being flexible and generally resulting in higher power conversion efficiency at all loads levels than an analog controller. For a typical digital controller to perform well, however, it requires the detection of DCM which further requires sensing the output inductor current and detecting the zero-crossing point of the output inductor current. To accurately detect the zero-crossing point of the output inductor current, the output inductor current needs to be sampled at a high sampling rate, to be converted to the digital form, and to be compared with zero. This means high speed sampling, high resolution analog-to-digital conversion (“ADC”), and high speed comparison are required. All of these result in an increase in power consumption, and in the size and cost of the power delivery subsystem and the entire system. Moreover, the switching noise, which is introduced at instances of turning on and off of the converter switches (when the zero crossing and peak of inductor current occurs), makes it more difficult to detect the zero-crossing point of the output inductor current. Furthermore, the addition of the sensing circuit for the output inductor current may impact the accuracy of the sensed and sampled values of the output inductor current and may in turn impact the operation accuracy of the digital power converter.